Process for manufacturing a leathery material

ABSTRACT

A SIMULATED LEATHER IS PRODUCED FROM A LAY-UP OF A LAYER OF SOFT TWIST YARNS AND/OR SILVERS AND A BATT CONSISTING OF SIMILAR FIBERS. THE LAY-UP HAS TWO OR MORE KINDS OF HEAT SHRINKABLE SYNTHETIC FIBERS HAVING DIFFERENT SHRINKAGE PERCENTAGES. THE LAY-UP IS SUBJECTED TO NEEDLE PUNCHING, HEAT SHRINKING AND RESIN TREATMENT TO PROVIDE AN INTEGRATED LAYER HAVING A STRUCTURE SIMULATING THAT OF THE CORIUM OF LEATHER.

United States Patent l 3,595,721 PROCESS FOR MANUFACTURING A LEATHERY MATERIAL Tatsuji Hamano, Sugano, Ichikawa, Chiba Prefecture,

Japan, and Tomohisa lizuka, llchikawa-minami, lchikawa, Chiba Prefecture, Japan No Drawing. Filed Nov. 17, 1967, Ser. No. 683,775 Claims priority, applicafgogsgapan, Dec. 1, 1966,

J Int. lCl. D04h 13/00 US. Cl. 156-148 11 Claims ABSTRACT OF THE DISCLOSURE A simulated leather is produced from a lay-up of a layer of soft twist yarns and/ or slivers and a batt consisting of similar fibers. The lay-up has two or more kinds of heat shrinkable synthetic fibers having dififerent shrinkage percentages. The lay-up is subjected to needle punching, heat shrinking and resin treatment to provide an integrated layer having a structure simulating that of the corium of leather.

This invention relates to the manufacture of simulated leather.

According to the present invention there is provided a process for manufacturing leather-like material, which comprises forming a lay-up (or assembly) of a layer consisting of soft twist yarns and/or slivers and a mixed batt consisting of fibers similar in kind thereto, said soft twist yarns and/ or slivers being various fibers mixed with two or more kinds of heat shrinkable synthetic fibers varying in percent shrinkage, thereafter passing the layup through a needle punching and heat shrinking treatment, and finally subjecting the lay-up to resin treatment to impart the effects of binding and filling thereto.

The product of this invention is soft in texture, yet exhibits outstanding toughness, flexibility, air permeability and water resistance. Furthermore, it not only exhibits a fiber structure similar to that of the corium of well-tanned genuine leather, but also has properties superior to those of other products of its kind, thus permitting far wider applications as a leather-like material.

A wide variety of studies have been carried out heretofore in an effort to develop a substrate of high quality for use in the manufacture of synthetic leather, but all prior attempts have failed to achieve a satisfactory result.

All currently available non-woven fabrics when used as substrates for synthetic leather, have been found to lack the required strength. An attempt to increase the strength of the materials requires larger amounts of resin adhesion through resin treatment, as well as stronger binding power. As a result, such non-woven fabrics tend to become stiff and lack both the hand and the character essential to high quality fabrics. The consequence of attempts to increase the softness of non-woven fabrics via resin treatment is that the fabric will be stretched, with a resulting decrease in strength and increased roughness, and an insertion of a layer of :woven fabric was necessary to avoid these difficulties.

In this invention, the foregoing difficulties are avoided by constructing the fibers of the lay-up in a manner similar to the three-dimensional cross-grained arrangement exhibited by the corium, i.e., true (inner) skin of genuine leather. That is, soft yarns and/or slivers of various fibers mixed with two or more kinds of heat shrinkable synthetic fibers are woven into a singleor multi-layer fabric in a crosswise fashion in a three dimensional structure having the desired thickness. This forms a base layer. The term soft twisted yarns means yarns intended for soft-surfaced fabrics which are given only a slack twist.

Superimposed upon this base layer is a batt, formed from various fibers mixed with two or more kinds of ice heat shrinkable synthetic fibers. The fibers of the batt are oriented diagonally to those of the cross-grained base layer. Subsequently, the lay-up is subjected to a needle punching operation, the needles being directed at various angles to the surface of the lay-up, and finally, to a heat shrinking treatment, such as utilizing hot water, steam, or dr heat.

Thus, the fibers of the lay-up become disoriented, and, correspondingly, their density increases. These interconnected fibers display the three-dimensional cross-grained arrangement observed in well-tanned leather.

The density of the fibers of the lay-up is increased by first impregnating them with a resin solution; thereafter, the lay-up is subjected to heating under pressure. The synthetic resin solution comprises two organic compounds, the first being a poor solvent for resin and the second being a poor solvent for the fibers of the lay-up, the boiling point of the first compound being higher than that of the second compound.

After the layup is impregnated with the synthetic resin solution, it is treated with a liquid coagulating agent :which is a poor solvent for both the fibers and the synthetic resin but which is miscible with the poor fiber solvent used in said synthetic resin solution, whereby said resin is rapidly and evenly deposited throughout the structure of the lay-up. Immediately after the deposition, the lay-up is quickly dried to recover said coagulating liquid and the organic compound dissolved therein, the resin in part adhering to the fibers with the remainder serving as a filler. Thus, a tough, but soft, leathery material is manufactured.

Illustrative of the various fibers, including heat shrinkable synthetic fibers, forming the soft twist yarns and slivers used in this invention are synthetic fiber filaments, staple fibers and crimped fibers, such as those made from polyamides, polyesters, polyacrylonitriles, polyvinyl alcohols, polypropylenes, polyethylenes, polyureas, etc., as well as natural fibers such as cotton and wool.

The mixing ratio of fibers to heat shrinkable synthetic fibers will be in the range of approximately :20 to 30:70, and more preferably will be between 70:30 and 50:50. The denier will preferably be 6 or less.

In order to prevent breakage of yarns during the weaving operation, fibers, 10 to about 20 cm. in length, will be mixed with those less than 10 cm. in length, in a ratio of 10 to 40% of the former and to 60% of the latter. For use in the lay-up of this invention, the mixed yarns should have a twist constant of not greater than 2.0, and are formed into soft twist yarns. The twist constant is represented by the formula:

Number of twists per inch (Count of Yarn) As used in the preceding equation, the count of yarn is the number of units of length per unit weight. Thus, in the metric system the count of yarn is measured as the length in kilometers of l kilogram of yarn.

The term slivers as used in this invention is defined as staple fibers loosely assembled in the form of an untwisted strand or rope. Soft twist yarns having twist constant of 1 or less, or slivers, should preferably be brought parallel to and twisted together with, or coiled around continuous yarns, such as multifilaments or monofilaments, prior to being used in this invention. Continuous yarns include synthetic fibers as used in soft twist yarns and natural fibers, such as silk, or regenerated fibers such as acetate rayon and viscose rayon. The preferred continuous yarns are heat shrinkable synthetic fibers, or fibers soluble in hot water or solvents, or fusible fibers.

Soluble fibers or fusible fibers, as used herein, are selected according to the nature of the heat shrinking treatment. For example, when hot water or steam is used, non-Formalin-reacted polyvinyl alcohol fibers, soluble at a temperature of 90 C., or below, may be used as continuous yarns. When steam or dry heat is applied, polyethylene fibers having a relatively low melting point are used. If

occasion demands such fibers as are soluble in a solvent used in a process other than the heat shrinking treatment, e.g., in the resin treatment, may be used. For example, when dimethylformamide is used in the resin treatment, continuous yarns of polyacrylonitrile fibers or urethane fibers, which are coiled around soft twist yarns or slivers, are dissolved. As a result, only the staple fibers will remain interconnected in a three dimensional multi-layered structure. There is yet another way designed to dissolve the continuous yarns. An acetone solution will dissolve acetate rayon or acrylonitrile fibers consisting of copolymers of acrylonitrile and vinyl chloride.

The base layer, formed with soft twist yarns or slivers, may be woven into plain, twill, or novelty fabrics, or textile fabrics of singleor multi-layers having a three-dimensional structure consisting of a combination of fabric constructions.

The batt is formed from fibers similar to those used for the soft twist yarns. The fibers constituting the batt are arranged in a parallel, crosswise, or random pattern. Since the base layer on which the batt is superimposed is constructed in a crosswise fashion and in a three-dimensional structure, it is preferred that the fibers of the batt are arranged at an angle of less than 90 with reference to the cross grain of the base layer. Such a batt is prepared by a carding machine or a random webber.

The lay-up, formed by laying the batt on the base layer consisting of soft twist yarns or slivers, is processed by a needle punching machine. The needles are applied in a reciprocal manner to the surface of the lay-up in either a perpendicular direction or a combination of perpendicular and non-perpendicular directions. Thus, the needles, alternately punching both faces of the lay-up, force the fibers of the batt and base layer into one another, thereby destroying the grain pattern of each individual layer so as to produce a single, completely integrated layer. In other Words, the result of this operation is that the soft twist yarns 'become interconnected with the various other fibers so that a completely integrated product having a crossgrained three-dimensional structure is formed.

Following the punching operation, the integrated layer is subjected to a heat shrinking process, which is generally performed with hot water, steam or dry heat. Preferably, the hot water should be at a temperature of 80 to 100 C., the steam at 100 to 180 C., and dry heat at 120 to 230 C. The period of the heat treatment will depend upon the shrinking method utilized: hot water or steam, to 60 seconds; dry heat, 1 to 10 minutes. Although the layup contains two or more kinds of heat shrinkable synthetic fibers, the fibers are so completely integrated with one another that a gradual and even shrinkage can be effected.

With the increased fiber density and the subsequent resin process, the lay-up takes on the appearance of a three dimensional structure wherein the fibers are arranged as in the corium of genuine leather, where interconnected collagen fibers are arranged in bundles in net-like layers.

After the heat shrinking treatment, the assembly is subjected to a resin treatment consisting of two steps. The first resin treatment may be performed by any of several conventional methods, such as immersion or spraying. Preferably, the amount of resin adhesion is in the range of 2% to 10% of the total fibers 'by weight. The resin to be used in the first step can be a synthetic rubber consisting of a carboxylated copolymer of acrylonitrile and butadiene, a nylon resin, an acrylic resin, a polyurethane resin, etc., in an emulsion or in a solution comprising an organic solvent.

After this process, the lay-up in the wet state, is subjected to a heat and pressure operation to be carried out at a temperature of 120 to 160 C. under .a pressure of 1 kg./cm. to 10 kg./cm. The specific gravity having increased as a result of the previous operation is now 0.20 to 0.33.

The second step of the treatment comprises dipping the lay-up in a synthetic resin solution comprising one or more solvents which will not dissolve the fibers and an organic compound which will not dissolve the resin, said organic compound having a boiling point higher than that of the organic solvent or solvents. Excess impregnated solution is removed with a press roll so that the amount of resin adhesion is reduced to the range of 10% to 40% of the total fibers, by weight. A liquid coagulating agent, soluble in the organic resin solvent or solvents is immediately added, thereby rapidly and evenly depositing the resin throughout the lay-up. The usual period for resin deposition is from 0.5 minute to 10 minutes. Finally, the lay-up is quickly dried to recover the solvent, part of the resin adhering to the fibers and remainder serving as a filler. Thus, a tough, but soft, leathery material is obtained.

It is preferred that a polyurethane resin be used in the second resin treatment. It is further preferred that the polyurethane resin be manufactured from a polyester, preferably used in excess of the stoichiometric requirements, and a polyisocyanate, said polyester being preferably obtained through the reaction of a dicarboxylic acid and a polyol, thereby forming a polyester having terminal hydroxyl groups. Suitable dicarboxylic acids include saturated fatty acids, e.g., adipic acid, sebacic acid, succinic acid, and unsaturated fatty acids, such as maleic and fumaric acids. Suitable polyols include diols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and butylene glycol, as well as triols, such as trimethylol propane, trimethylol titanium, hexane triol and glycerine. By varying the combination of dicarboxylic acid and polyol, various kinds of polyesters are obtained, but the most preferred polyester is obtained from the reaction of adipic acid and diethylene glycol. The preferred diisocyanates to be reacted with the polyester are 2,4-toluene diisocyanate and 4,4'-diisocyanate diphenyl-methane.

The polyurethane resin is preferred formed by reacting a small amount of a triol to a mixture of diisocyanate and an excess of polyester, whereby a polyurethane deadpolymer is obtained, said deadpolymer having no terminal NCO groups but a number of cross-linkages.

Alternatively, the polyester may be reacted with an excess of diisocyanate in order to produce a prepolymer having -NCO groups at both terminals, to which a small amount of diamine, such as hydrazine or ethylene diamine, is added, thereby reacting the isocyanate groups with the amino compound to obtain urea linkages. Then the terminal isocyonate groups of the remaining ureacted prepolymer react with the urea linkages, thereby forming a polyurethane elastomer having biuret cross-linkages.

Another method comprises reacting a diol With an excess of diisocyanate to form a prepolymer having NCO groups at both terminals. A second prepolymer having terminal -OH groups is prepared by the reaction of a dicarboxylic acid, a diol, and a triol. This second prepolymer is reacted with an excess of diisocyanate to prepare a prepolymer having NCO groups at both terminals. Then a mixture of the two kinds of prepolymers is prepared and both are simultaneously subjected to a foaming reaction and cross-linkage reaction in the subsequent polyurethane-forming process.

Suitable organic solvents that may be used in this invention as the poor fiber solvent are dimethyl formamide, acetone, methylethylketone, and toluene. As a coagulating liquid, water or methanol is used. As an organic compound which is a poor resin solvent and whose boiling point is higher than that of said organic solvents, a solution comprising 2% to 10% polyol by Weight is used.

In the prior art the resin is prevented from adhering to the fibers by extracting the solvent with water. However, in a specific embodiment of this invention, the layup, which is impregnated with a solution of a polyurethane resin having no terminal -NCO groups, and a polyol having a higher boiling point than dimethylformamide, is treated with water so as to deposit said resin, evenly and rapidly, throughout the fabric structure.

Subsequently, as water is first removed by drying, part of the coagulated resin is dissolved in part by the residual dimethylformamide, and acts as a binder. A larger part of the resin, however, remains coagulated without being dissolved, and serves as a filler, because the resin solvent, dimethylformamide, is more readily recovered than the higher boiling polyol in the drying process. Hence, the product of this invention is not only low in production cost, but also avoids the problem of water pollution.

The lay-up treated as specified hereinbefore, is usually further subjected to splitting and/ or buffing and any conventional finishing process. The resulting material is of an excellent, leather-like quality, having a soft texture as Well as outstanding toughness, flexibility, air permeability and water resistance.

The following specific examples are given by way of illustration of this invention, and not limitation.

EXAMPLE 1 A s soft twist yarn having a twist constant of 2 is prepared by mixing 20% of S-centimeter long and 3- denier crimped polyamide fibers with 30% of -centimeter long and 1.5-dienier crimped polyamide fibers, of 7-centimeter long and 3-denier polyamide fibers having a shrinkage value of 15% and of 7-centimeter long and 2-denier polyamide fibers having a shrinkage value of A 2/2 broken double layer fabric having a weight of 300 grams per square meter is woven with warps and woofs consisting of said soft twist yarn. The term 2/2 broken double layer fabric means that the warps are two upper and two lower each than the wefts in their warp direction and the wefts are two upper and two lower than the warps in their weft direction. This results in a two layer arrangement. A batt consisting of the same fiber composition as the soft twist yarn and having a weight of 80 grams per square meter is superimposed on the fabric to form a lay-up or composite.

The lay-up so manufactured is passed through a needling machine, wherein needling is performed alternately on both faces of the lay-up in perpendicular and slanting direction to the surface of the lay-up, at a rate of 200 needles per square centimeter. Through the needling operation, the fibers of the soft twist yarn are interlocked with those of the batt, thereby reducing the effects of twist of the twisted yarns. As the spaces between the yarns become smaller, the lay-up is further integrated and the fibers become arranged in bundles with a three dimensional structure.

After the needling operation, the lay-up is dipped in hot water for 30 seconds at a temperature of 92 C. so that it shrinks slowly and evenly to 65% of the total initial area.

In the first resin treatment, the lay-up is dipped in an emulsion solution comprising an acrylic resin of the selflinked type having carboxyl groups. The excess impregnated solution is removed bly passing the lay-up through a press roll so that the amount of resin remaining is reduced to 8% by weight of the total fiber weight.

After pre-heating at a temperature of 80 C. for the purpose of reducing its moisture content to 40%, the lay-up is heat-pressed under a pressure of 2 kilograms per square centimeter and at a temperature of 140 C. A fully dried high density lay-up is produced, having a specific gravity of 0.27.

The resin used in the second resin treatment consists of polyester, triol, and diphenylmethane-4,4'-diisocyanate and is prepared in the following manner: A stable polyurethane deadpolymer, which is partly cross-linked and has no terminal --NCO groups, is produced by first admixing a mole of the polyester (said polyester being formed from adipic acid and diethylene glycol having terminal OH groups and a molecular weight of about 2,000) with a mole of diphenylmethane-4,4' diisocyanate and 0.15 mole of trimethylol propane, and thereafter heating the mixture for 4 hours at a temperature of C. As the VlSCOSllJY increases during the reaction, anhydrous dimethylformamide is slowly added to the polyurethane deadpolymer beginning at about 20 minutes after the reaction has started so that viscosity reaches about 900 to 1,000 poises. Enough polyurethane deadpolymer is dissolved in dimethylformamide to form a 20% solution, to which a 5% solution of polyethylene glycol having a molecular weight of 3,000 is added.

After heating under pressure, the lay-up is dipped in the resin solution twice and thereafter passed through the press roll until the deposition of the resin constitutes 25% of the total fiber content by weight. Then the layup is dipped in water for one minute to deposit the polyurethane deadpolymer evenly on and between the fibers, and is then dried at a temperature of C.

The water serving as a coagulating liquid evaporates during the drying process, and the dimethylformamide which is a solvent for the resin remains. Part of the resin is dissolved in the remaining solvent, but a greater part of the resin remains coagulated because of the presence of polyethylene glycol which is a non-solvent for the resin and higher in boiling point than the dimethylformamide, the difference in boiling points thus permitting more rapid elimination of dimethylformamide than of said polyol.

The lay-up so manufactured is subjected to finishing such as splitting and buffing. Finally, a tough but soft leather-like material having a good air permeability is produced.

EXAMPLE 2 A 6s sliver is prepared by mixing 20% of S-centimeter long and Z-denier crimped polyamide fibers with 20% of lZ-centimeter long and 3-denier crimped polyamide fibers, 20% of ZOcentimeter long and B-denier crimped polyamide fibers, 20% of 6-centimeter long and 2-denier polyester fibers having a shrinkage value of 20%, and 20% of S-centimeter long and 2-denier polyester fibers having a shrinkage value of 40%.

Next, a 120-denier water soluble polyvinyl alcohol multifilament consisting of twenty 6-denier multifil'arnents is coiled around said sliver at a rate of 30 turns per 10 centimeters and care is taken not to permit the sliver to twist.

A 3/1 broken warp double fabric having a weight of 250 grams per square meter is woven with the slivers manufactured as specified above. Upon the fabric a batt having a weight of 100 grams per square meter and consisting of the same fiber composition as the slivers is superimposed in a manner such that the fibers of the batt are in a direction diagonal to those of the fabric.

The lay-up so manufactured is subjected to a needling operation, wherein the needling is performed alternately on both faces of the lay-up with needles in the direction perpendicular to the surface of the lay-up at a rate of needles per square centimeter. Through this needling operation, the fibers of the slivers and the batt are interlocked together.

After this needle-punching operation, the lay-up is dipped in hot water for 60 seconds at a temperature of 95 C., and the water soluble polryvinyl alcohol multifilaments coiled around the slivers are dissolved, while the slivers remain unaffected. Through this hot Water dipping, the lay-up shrinks slowly and evenly to 60% of the total initial area.

The lay-up is subjected to the first resin treatment and the heating under pressure operation in the same manner as in Example 1.

To produce the resin for the second resin treatment, a prepolymer having terminal -NCO groups is first prepared by admixing one mole of polyester having a molecular weight of 1,500 and terminal OH groups with 1.5 moles of diphenylmetha'ne 4,4-diisocyanate, and heating the mixture for 3 hours at a temperature of 85 C. As the viscosity increases during the reaction, anhydrous dimethylformamide is added so that the viscosity remains at 600 poises.

Next, 0.2 mole of ethylene diamine dissolved in dimethylformamide is added to the above prepolymer solution, thereby reacting the isocyanate groups with the amino groups to form urea linkages. Afterwards, the prepolymers terminal -NCO groups are reacted with the urea linkages at a temperature of 130 C, thereby forming a partly cross-linked polyurethane deadpolymer through the biuret linkages.

A deadpolymer solution is prepared by dissolving the above polyurethane deadpolymer in the dimethylformamide, to which 8% of polypropylene glycol having a molecular Weight of 2,500 is added. After the above-mentioned heat pressure operation, the lay-up is dipped twice in the resin solution, and thereafter subjected to a press roll so that the amount of the resin adhesion constitutes 30% by weight of the total fiber weight. Then the resultant lay-up is dipped in water for 3 minutes to deposit the polyurethane deadpolymer evenly on and between the fibers. Through the same treatment as specified in Example 1, a leather-like material is produced.

EXAMPLE 3 A 3s sliver is prepared by admixing 30% of S-denier Wool With of l6-centimeter long and Z-denier polyester fibers, 15% of 7-centimeter long and 3-denier polyester fibers having a shrinkage value of 15%, and of 7-centimeter long and 3-denier polyester fibers having a shrinkage value of Next, a 80-denier acetate rayon multifilament consisting of twenty 4-denier multifilaments is coiled around the sliver at a rate of 25 turns per 10 centimeters by taking care not to allow the sliver to twist.

A 2/2 twill weave single layer fabric having a weight of 200 grams per square meter is Woven with the slivers as specified above. A batt having a Weight of 80 grams per square meter and consisting of the same fiber composition as the sliver is superimposed on the fabric in a manner such that the fibers of the batt are in the direction diagonal to those of the fabric.

The lay-up so manufactured is subjected to a needling operation, wherein the needling is performed alternately on both faces of the lay-up with needles in perpendicular and slanting directions to the surface of the lay-up at a rate of 150 needles per square centimeter. Through this needling operation, the fibers of the slivers and the batt are interlocked together.

After this needle-punching operation the lay-up is dipped into hot water at a temperature of 96 C. for seconds, thus effecting slow and even shrinkage to of the total initial area.

In the first resin treatment, the resultant lay-up is dipped in an acetone solution prepared by adding a small amount of dibutyltin-dilaurate, as a catalyst, to a polyether urethane prepolymer, and passed through a press roll to remove the excess portion of the impregnated solution so that the amount of resin adhesion constitutes 3% by weight of the total fiber weight. At the same time, the acetate rayon multi-filaments are dissolved and the lay-up results in having fiber bundles with a three-dimensional structure. The Wet lay-up is heat-pressed under a pressure of l kilogram per centimeter at a temperature of 130 C., and thereby transformed into a well dried lay-up having a high density and a specific gravity of 0.30.

To produce the resin for the second resin treatment, a prepolymer having terminal --NCO groups is first prepared by admixing one mole of polyester having a molecular weight of 1,000 and terminal OH groups with 1.1 mole of diphenylmethane-4,4-diisocyanate, and heating the mixture for 2 hours at a temperature of 80 C. A second prepolymer is prepared by causing one mole of polyester to react with 3 moles of 2,4-toluenediisocyanate, said polyester consisting of adipic acid, diethylene glycol,

and trimethylol propane. The two above-mentioned types of prepolymers and a small amount of dibutyltin dilaurate are dissolved in an acetone solution. After being dipped in the solution, the lay-up is passed through a press roll so that the quantity of resin adhesion constitutes 20% by weight of the total fiber weight. Following this process, the resulting lay-up is dipped in Water to deposit polyurethane evenly on and between the fibers thereby causing a foaming reaction and cross-linkages at the same time, Through the same treatment as specified in Example 1, a leather-like material is produced.

EXAMPLE 4 An 8s yarn in which the first twists are 40 turns per 10 centimeters is prepared by mixing 30% of 7-centimeter long and 3-denier crimped polyester fibers with 30% of l2-centimeter long and Z-denier crimped polyester fibers, 20% of 8-centimeter long and 3-denier polyester fibers having a shrinkage value of 20%, and 20% of 8-centimeter long and 3-denier polyester fibers having a shrinkage value of 35%.

Next, by twisting said 8s yarn with a l40-denier polyethylene multifilament consisting of twenty 7-denier multifilaments at a rate of 30 second twists to form a soft twist yarn having a twist constant of 1.

A three-layer fabric having a weight of 350 grams per square meter is woven with the yarn. Then a batt having the same fiber composition as the soft twist yarn and a weight of 50 grams per square meter is superimposed upon the fabric.

The lay-up so manufactured is passed through a needling machine, wherein needling is performed alternately on both faces of the lay-up with the needles in the direction perpendicular to the surface of the lay-up at a rate of 200 needles per square centimeters.

After the needling operation, the lay-up is subjected to a dry heat shrinking process at a temperature of 180 C. Through this process the polyethylene multifilament is fused, and the lay-up shrinks slowly and evenly to 60% of the total initial surface area. The first resin treatment and the subsequent process are conducted in such a manner as specified in Example 1.

EXAMPLE 5 A 12s soft twist yarn having a twist constant of 1.0 is prepared by admixing 30% of S-Centimeter long and r-denier crimped polyacrylonitrile fibers with 15% of 12- centimeter and 3-denier polypropylene fibers, 15 of 16- centimeter long and 3-denier polypropyrene fibers, 20% of 7-centimeter long and 2-denier polyester fibers having a shrinkage value of 15%, and 20% of 7-centimeter long and 2-denier polyester fibers having a shrinkage value of 35%.

The soft twist yarn is put together with a -denier heat shrinkable polyamide multifilament consisting of twenty 4-denier multifilaments to form a woof. A Warp is prepared by first forming a 8s sliver having the same fiber composition as above, and twisting the sliver with said 80-denier heat shrinkable polyamide multifilament at a rate of 10 twists per 10 centimeters. A single-layer plain fabric having a weight of 250 grams per square meter is woven with the warp and the woof manufactured as above. Then a batt consisting of the same fiber composition as specified hereinbefore and having a Weight of 80 grams per square meter is superimposed on the fabric in a manner such that the fibers of the batt are in the direction diagonal to those of the base fabric. The resultant lay-up is treated as specified in Example 3.

We claim as our invention:

1. A process for manufacturing an imitation leather material, which comprises the steps of:

(1) superimposing a mixed batt upon a woven fabric base layer to form an assembly, wherein the fibers of said mixed batt are oriented diagonally to the fibers of said woven fabric base layer, the fibers of said woven fabric base layer and of said mixed batt being selected from the group consisting of soft twist yarns having a twist constant not greater than 2.0 and slivers, said fibers of said woven fabric base layer and of said mixed batt comprising at least two kinds of heat-shrinkable fibers having difierent heat shrinkage percentages and non-heat-shrinkable fibers in a weight ratio of heat-shrinkable fibers to non-heatshrinkable fibers in the range of 20:80-70:30;

(2) punching said assembly with needles;

(3) heat-shrinking said assembly;

(4) impregating said assembly with a solution comprising a first resin;

(5) heating said assembly under pressure whereby the specific gravity increases;

(6) immersing said assembly in a solution comprising a second resin, at least one poor fiber solvent, and an organic compound which is a poor resin solvent having a higher boiling point than said poor fiber solvent;

(7) coagulating said second resin with a liquid soluble in said poor fiber solvent; and

(8) drying said assembly.

2. The process according to claim 1, wherein the dried assembly is subjected to a finishing treatment.

3. The process according to claim 1, wherein said soft twist yarns have a twist constant of 1.0 or less and are intimately arranged together with continuous yarns, said soft twist yarns consisting of at least one fiber selected from the group consisting of synthetic fibers and natural fibers in admixture with at least two synthetic fibers having different heat shrinkage percentages.

4. The process according to claim 1, wherein said slivers are intimately arranged with continuous yarns, said slivers comprising at least two synthetic fibers having different heat shrinkage percentage.

5. The process according to claim 3, wherein said continuous yarn is a synthetic fiber which is capable of being dissolved in a step subsequent to said needle punching.

6. The process according to claim 4, wherein said continuous yarn is a synthetic fiber which is capable of being dissolved in a step subsequent to said needle punching.

7. The process according to claim 1, wherein 1040% by weight of the fibers comprising said soft twist yarns and said slivers are from 10 to centimeters long.

8. The process according to claim 1, wherein the fibers are selected from the group consisting of wool, cotton, acetate rayon, viscose rayon, polyethylene, polyamide, polyester, polyvinyl alcohol, polyacrylonitrile and polypropylene fibers, said first resin is selected from the group consisting of acrylic resins, synthetic rubber, polyamide 10 resin and polyurethane resins, and said second resin is at least one polyurethane resin.

9. The process according to claim 8, wherein the poor fiber solvent is selected from the group consisting of dirnethyl formamide, acetone, methylethylketone and toluene, the organic compound is a polyol, and said liquid soluble in said poor fiber solvent is selected from the group consisting of water and methanol.

10. The process according to claim 8 wherein the fabric consists of soft twist yarn which has a twist constant of 2 and is prepared from 20% crimped 3-denier polyamide fibers, 30% crimped 1.5 denier polyamide fibers of 15% shrinkage value and 30% 2-denier polyamide fibers of 40% shrinkage value, the batt consists of the same fiber composition as the fabric, heating is carried out at 92 C. in water, an acrylic resin of the self-linked type having carboxyl groups is used in the first resin treatment, and the resin in the second resin treatment consists of a polyurethane from diphenylmethane-4,4'- diisocyanate and the polyester from adipic acid and diethylene glycol.

11. The process according to claim 4 wherein the fabric consists of slivers prepared from 20% Z-denier crimped polyamide fibers, 20% 3-denier crimped polyamide fibers, 20% 3-denier crimped polyamide, 20% 2-denier polyester fibers of 20% shrinkage value and 20% Z-denier polyester fibers of 40% shrinkage value with polyvinyl alcohol multifilaments, the batt is of the same composition as the fabric, the resin in the first treatment is an acrylic resin of the self-linked type containing carboxyl groups and the resin in the second treatment is the polyurethane from diphenylmethane-4,4-diisocyanate with a polyester containing terminal -OH groups, and reacting the prepolymer thus formed with ethylene diamine.

References Cited UNITED STATES PATENTS 2,253,000 8/1941 Francis 156-148X 2,417,453 3/1947 Wade 156-148X 2,737,701 3/1956 Hubbard et al. 156148X 2,869,974 1/1959 Adams 2872.2X 2,869,975 1/1959 Hare 2872.2X 2,881,505 4/1959 Hoffman 2872.2X 2,978,785 3/1961 Wenzell 2872.2X 3,407,461 10/1968 Stevenson et a1. 28--72.2

CARL D. QUARFORTH, Primary Examiner G. G. SOLYST, Assistant Examiner US. Cl. X.R. 2872.2; 156--3l4 

